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DIY 47mm Acrylic Whatman Filter Plates

We use a couple of glass 3 piece Whatman filter funnels in the lab at work to filter used oil samples before testing. A glass fibre filter paper is supported by an acrylic plate and samples are drawn through it into a vacuum flask below. When someone decided it was a good idea to clean the acrylic plate in acetone, it was wrecked and our labware supplier wanted £40 for a new 47mm Whatman filter plate.

Being just a piece of acrylic with a few dozen small holes in it Lizzy suggested I laser cut a new one rather than us paying for and waiting for it. The resulting plate was usable the same day and at a tenth of the cost. It works just as well! If you want one, leave a comment.

Photos and files after the break.

The part was drawn first in Alibre, converted to a 2D drawing then to a .dxf file. The holes I measured from a bigger, non-wrinkled filter plate as being 0.8mm in diameter. I set mine to 0.7mm in the drawing to allow for the laser cutter kerf. (click the image below to enlarge)

I used 6mm thick acrylic, cutting it on the laser with power 98/100 and speed 3/400 for the outside and 2/100 for the holes. The laser takes time to penetrate hence why I slowed the cut down for the holes and added a 0.5mm overlap in the cutting settings.

A blast from the air line after cutting cleared out the remaining acrylic residue. Ready for a test run!

With an unusual lack of used oil in the lab, we tested it with some Brasso diluted with white spirit. The white spirit came out clean and all of the Brasso particles were left on the filter paper. It didn’t look like the filter paper was damaged in any places, which would have happened had the holes been too big.